Advanced oxidation processes (AOPs), defined as those technologies that utilize the hydroxyl radical (·OH) for oxidation, have received increasing attention in the research and development of wastewater treatment technologies in the last decades. These processes have been applied successfully for the removal or degradation of toxic pollutants or used as pretreatment to convert recalcitrant pollutants into biodegradable compounds that can then be treated by conventional biological methods. The efficacy of AOPs depends on the generation of reactive free radicals, the most important of which is the hydroxyl radical (·OH). The authors summarize the formation reactions of ·OH and the mechanisms of pollutants degradation. They cover six types of advanced oxidation processes, including radiation, photolysis and photocatalysis, sonolysis, electrochemical oxidation technologies, Fenton-based reactions, and ozone-based processes. Controversial issues in pollutants degradation mechanism were discussed. They review t...

Advanced Oxidation Processes for Wastewater Treatment: Formation of Hydroxyl Radical and Application

Sonochemical engineering is a field involving the application of sonic and ultrasonic waves to chemical processing. Sonochemistry enhances or promotes chemical reactions and mass transfer. It offers the potential for shorter reaction cycles, cheaper reagents, and less extreme physical conditions, leading to less expensive and perhaps smaller plants. The amount of things that can be accomplished with sonochemistry is, at this stage, only limited by the minds of those working in this exciting field. Existing literature on sonochemical reacting systems is chemistry-intensive, and applications of this novel means of reaction in environmental remediation and pollution prevention seem almost unlimited. For example, environmental sonochemistry is a rapidly growing area that deals with the destruction of organics in aqueous solutions. However, some theoretical and engineering aspects are not fully understood. This paper reviews the field comprehensively by combining the existing knowledge from chemistry with insi...

Sonochemistry: Environmental Science and Engineering Applications

Etude de la structure d'un catalyseur utilise pour une hydrodesulfuration et plus particulierement etude de la localisation et de la structure des ions molybdene et cobalt a la surface de l'alumine. Discussion sur le role d'un promoteur modifiant un catalyseur, notamment determination du nombre de sites actifs

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Structure and Function of the Catalyst and the Promoter in Co—Mo Hydrodesulfurization Catalysts

Free radical formation induced by ultrasound and its biological implications

The physical principles underlying the oscillatory behavior of minute gas bubbles in liquids exposed to ultrasound are reviewed. Results from mathematical analyses suggest that these oscillations sometimes become unstable leading to transient cavitation in which a bubble violently collapses during a single acoustic half-cycle producing high temperatures and pressures. The role that micronuclei, resonant bubble size, and rectified diffusion play in the initiation of transient cavitation is explained. Evidence to support these theoretical predictions is presented with particular emphasis on sonoluminescence which provides some non-chemical evidence for the formation of free radicals. Acoustic methods for conducting sonochemical investigations are discussed. In aqueous solutions transient cavitation initially generates hydrogen atoms and hydroxyl radicals which may recombine to form hydrogen and hydrogen peroxide or may react with solutes in the gas phase, at the gas-liquid boundary or in the bulk of the solution. The analogies and differences between sonochemistry and ionizing radiation chemistry are explored. The use of spin trapping and electron spin resonance to identify hydrogen atoms and hydroxyl radicals conclusively and to detect transient cavitation produced by continuous wave and by pulsed ultrasound is described in detail. The study of the chemical effects of cavitation in organic liquids is a relatively unexplored area which has recently become the subject of renewed interest. Examples of the decomposition of solvent and solute, of ultrasonically initiated free-radical polymerization and polymer degradation are presented. Spin trapping has been used to identify radicals in organic liquids, in polymer degradation and in the decomposition of organometallic compounds.

Free radical generation by ultrasound in aqueous and nonaqueous solutions.

Sonolysis of water at 447 kHz causes a decrease in the pH. The products formed depend to some extent on the nature of the dissolved gases; products observed are hydrogen peroxide, nitrous and nitri...

The effect of ultrasound on water in the presence of dissolved gases

Some ring replacement and nucleophilic substitution reactions of η6-subsituted arene-η5-cylopentadienyliron hexafluorophosphates

Ligand exchange of some heterocyclic analogues of fluorene and anthracene with ferrocene

The reaction of 9,10-dimethylanthracene (8) with ferrocene (FcH) in the presence of AlCl3–Al in decalin gave the stereospecifically hydrogenated product, η6-cis-(endo-9,10-dihydro)-9,10-dimethylanthracene-η5-cyclopentadienyliron cation (10a), the hydrogenation at C-9,10 being cis and endo or on the same side as the cyclopentadienyliron (CpFe) moiety. When cis-9,10-dihydro-9,10-dimethylanthracene, generated from 10a by photolysis or pyrolytic sublimation, was used as the arene in the ligand exchange reaction, complexing with the CpFe group could occur from either side of the ring system, giving rise to a mixture of 10a and the η6-cis-(exo-9,10-dihydro)-9,10-dimethylanthracene-η5-cyclopentadienyliron cation (10b). The η6-cis-9,10-dihydro-9,10-dimethylanthracene-trans-bis-η5-cyclopentadienyliron dication, with the two CpFe groups trans, was also prepared either from a stepwise ligand exchange using 10a or directly from reaction of 8 using an excess of FcH. A mechanism is proposed for the hydrogenation that h...

R.G. Sutherland

Papers

The effect of ultrasound on water in the presence of dissolved gases

Some ring replacement and nucleophilic substitution reactions of η6-subsituted arene-η5-cylopentadienyliron hexafluorophosphates

Ligand exchange of some heterocyclic analogues of fluorene and anthracene with ferrocene

Ligand exchange reactions between ferrocene and 9,10-dimethylanthracene

Studies on nucleophilic substitution reactions with η6-o-dichlorobenzene-η5-cyclopentadienyliron hexafluorophosphate